1. Field of the Invention
The present invention relates to a method of programming an interactive numerical control apparatus, and more particularly to a method of programming an interactive numerical control apparatus for simultaneous generation of numerical control (NC) data for primary and secondary machining operations.
2. Description of the Related Art
When interactive numerical control apparatus are to be programmed, the operator Inputs numerical data in answer to questions as to necessary items according to a procedure, or selects a desired Item from a displayed menu. Such an interactive programming method is widely used to generate machining programs for various numerically controlled machine tools because it allows even novice operators to generate the programs by using data from drawing figures and other sources.
Some interactive numerical control apparatus employ symbolic keys for entering shape elements to input blank and part shapes. Specifically, the shape of a part is inputted using horizontal lines, vertical lines, oblique lines, and arcs to generate a machining program. The use of such symbolic keys allows part shapes to be inputted easily for efficient generation of NC programs.
Computerized, numerically controlled lathes with a plurality of machining heads for higher machining efficiency include a two-spindle, two turret four-axis lathe having two parallel spindles. Usually, a workpiece is machined by the two-spindle, two-turret four-axis lathe such that one end of the workpiece, which is held by one of the heads, is machined in a primary machining operation, and thereafter the workpiece is held by the other head and its opposite end is machined in a secondary machining operation (which may also be referred to as a backward machining operation).
FIG. 11 of the accompanying drawings schematically shows the manner in which a workpiece is machined by a two-spindle, two-turret four-axis lathe. First, a workpiece 42a held by a chuck 41a is machined to a desired shape by a tool 44a mounted on a turret 43a in a primary machining operation. Then, the machined workpiece 42a is released from the chuck 41a and held, as a workpiece 42b, by another chuck 41b. The workpiece 42b held by the chuck 41b is machined to a desired shape by a tool 44b mounted on a turret 43b in a secondary machining operation.
According to the conventional method of programming interactive numerical control apparatus, NC data for a primary machining operation and NC data for a secondary machining operation are generated separately from each other. Therefore, the interactive numerical control apparatus must be programmed separately on the NC data for the primary and secondary machining operations even if one final part shape is to be achieved. Such a programming process has been inefficient to carry out.